Development of Graphene-Filled Fluoropolymer Composite Coatings for Condensing Heat Exchangers

Low-temperature waste heat recovery employs condensing heat exchangers to recover both sensible and latent heats. Due to the condensation of flue gases within these heat exchangers, they are subjected to severe corrosion. Perfluoroalkoxy (PFA) has been applied as a barrier layer on the surfaces of these heat exchangers for the prevention of corrosion. However, PFA has exhibited poor thermal properties and durability, which are requirements in low-temperature heat recovery applications. In this thesis, carbon-based nano-materials (8 nm and 60 nm thickness graphene particles and multi-walled carbon nanotubes, MWCNT) were incorporated into fluoropolymer (PFA) powders to generate thermally conductive and corrosion resistant composites as heat exchanger coatings. The microstructure, thermal conductivity, electrical conductivity of these composites were characterized. It was found that the thermal conductivities of the graphene-filled composites were significantly higher than that of the virgin PFA, i.e. approximately 8 times, while the composites containing MWCNT particles exhibited minimal improvement in thermal properties. The coatings containing both grades of graphene exhibited good surface finish and coating adhesion, good wear resistance and excellent corrosion resistance. The MWCNT-filled composites showed poor surface finish, resulting in poor corrosion resistance